Nueroprosthesis for Epileptic Seizures

The work involves a minuscule transmitter which is just three times the width of a human hair. The transmitter is designed to be implanted below the scalp in order to detect the signs of an epileptic seizure before it occurs.

The system records neural electrical signals relayed by electrodes in various points in the brain, said Pedro Irazoqui, assistant professor of biomedical engineering.

“When epileptics have a seizure, a particular part of the brain starts firing in a way that is abnormal,” Irazoqui said. “Being able to record signals from several parts of the brain at the same time enables you to predict when a seizure is about to start, and then you can take steps to prevent it.”

Data from the implanted transmitter will be picked up by an external receiver, also being developed by the Purdue researchers.

The most critical aspect of the research is creating a device that transmits a large amount of data at low power. The transmitter consumes 8.8 milliwatts, or about one-third as much power as other implantable transmitters while transmitting 10 times more data. Another key advantage is that the transmitter has the capacity to collect data specifically related to epileptic seizures from 1,000 channels, or locations in the brain, Irazoqui said.

“The fact that this circuit can deliver such a vast amount of data and, at the same time, be less power hungry than anything else that’s out there is what makes this important,” he said.

Clinical Trials under Way

The miniature transmitter and its battery will be implanted below the scalp, and electrodes which pick up data are to be inserted directly in the brain through holes in the skull, then connected to the transmitter by wires.

“That device can record from eight channels to collect epilepsy data, compared to a thousand channels for our system,” Irazoqui said. “The more parts of the brain that you can look at simultaneously, the better you are able to predict the seizure onset, so the number of channels has a direct correlation with how well the device works.”

Human testing in planned in two years. “Epilepsy affects about 1 percent of the global population, and of that 1 percent, 30 percent don’t respond to any drugs. There is no cure or treatment for those 30 percent.”

New technologies are under development with the goal of changing that. By predicting the onset of seizures and instantly dispensing the proper neurotransmitter chemical directly to the area of the brain where the seizure is starting, treatment for epilepsy, which effects 1% of the worlds population, could be revolutionized.

Neuroprosthesis Research

The research is part of a collaboration at Purdue focused on developing a neuroprosthesis to dispense a neurotransmitter called GABA. Its aim is to calm the brain once the onset of a seizure is detected, thus preventing an epileptic “focal seizure,” which starts in a specific area of the brain but can then quickly spread to the rest of the brain “like a brush fire,” Irazoqui said.

“Once you find out where that focal area is, if you know the seizure is about to start you can suppress the seizure,” he said. This undertaking is a collaboration between Irazoqui and Jenna Rickus, assistant professor of biomedical engineering.

Professor Rickus has invented a “living electrode” coated with specially engineered neurons that, when stimulated, releases GABA in order to inhibit the seizure. The engineered neurons are living tissue stimulated with a microchip. Certain levels of electrical current cause the neurons to release specific, controllable quantities of neurotransmitter.

“The idea is that by using an engineered cell to release a neurotransmitter, we have a drug pump, in essence, that automatically refills itself and that only impacts the part of the brain where the living electrode is implanted: the epileptic focus,” Irazoqui said. “So you are not going to get the side effects that you get by washing the entire body in a particular pharmaceutical.”